If you want to have a HVA on the "C" ring for sure, you will have to buy a M/146 (9.3X57).
Only a few HVA 640 rifles were built on "C" ring actions after WWII. The 640 series using the M/98 action started somwhere in 1946 and they fast started to omit the cut the thumb cut-out notch and the charger clip "hump" and lips, by the end of 1947, the actions were what will be known as the "commercial" version. By 1949, HVA introduced the '06 in the caliber range and by the same time the receivers were d&t for receiver sight.
But FN also changed the steel composition (to a much more modern one) of their barrels and receivers.
I use(d) both the "C" and "H" versions in many calibers including magnums and I still have to see a "H" ring to fail.
Only reason it may happen and it will also happe with the "C" rings, is if the rear of the lower receiver lug is ground to make room to a longer than "06 (3.340") range caliber.
If you want to buy a "real commercial" Mauser 98 action, you can look at Brno 21/22 "H" or "F", original Oberndorf (usually pretty expensive), Sako Hi-Power, Browning, FNH, J.C. Higgins and of course HVA, and there are many, many others too, such as Parker-Hale and Zastava....
But keep in mind that Holland & Holland are still building rifles on ex-military actions, so does Voere and others....